package com.bean;

import java.util.Arrays;

/**
 * 生成验证码字符
 */
public class CreateVerificationCode {
    /**
     * 验证码难度级别
     */
    public enum SecurityCodeLevel {
        Simple,
        Medium,
        Hard
    }

    public static String getSecurityCode() {
        return (String) getSecurityCode(4, SecurityCodeLevel.Medium, false);
    }

    public static String getSecurityCode(int length, SecurityCodeLevel level, boolean isCanRepeat) {
        int len = length;
        //除去容易混淆的0和o，1和l
        char[] codes = {
                '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                'j', 'm', 'n', 'p', 'q', 'r', 's', 't', 'u',
                'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E',
                'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S',
                'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
        if (level == SecurityCodeLevel.Simple) {
            codes = Arrays.copyOfRange(codes, 0, 9);
        } else if (level == SecurityCodeLevel.Medium) {
            codes = Arrays.copyOfRange(codes, 0, 33);
        }
        int n = codes.length;
        //抛出运行时异常
        if (len > n && isCanRepeat == false) {
            throw new RuntimeException(
                    String.format("调用securitycode.getSecurityCode(%1$s,len,level,isCanRepeat,n)"));
        }
        char[] result = new char[len];
        //判断能否出现重复的字符
        if (isCanRepeat) {
            for (int i = 0; i < result.length; i++) {
                //索引0 and n-1
                int r = (int) (Math.random() * n);
                //将result中的第i个元素设为codes[r]存放的数值
                result[i] = codes[r];
            }
        } else {
            for (int i = 0; i < result.length; i++) {
                int r = (int) (Math.random() * n);
                //将result中的第i个元素设为codes[r]存放的数值
                result[i] = codes[r];
                codes[r] = codes[n - 1];
                n--;
            }
        }
        return String.valueOf(result);
    }
}
